Optical sensors for monitoring biopharmaceutical solutions in single-use containers

ABSTRACT

Disposable, pre-sterilized, and pre-calibrated, pre-validated sensors are provided. The sensor comprises a disposable fluid conduit or reactor bag and a reusable sensor assembly. An optical bench or inset optical component is integrated within the disposable fluid conduit or bioreactor bag, which provides an optical light path through the conduit or bag. These sensors are designed to store sensor-specific information, such as calibration and production information, in a non-volatile memory chip on the disposable fluid conduit or bag and on the reusable sensor assembly. Methods for calibrating the sensor and for determining a target property of an unknown fluid are also disclosed. The devices, systems and methods relating to the sensor are suitable for and can be outfitted for turbidity sensing.

FIELD OF THE INVENTION

The invention generally relates to disposable, pre-sterilized,pre-calibrated, in-line sensors. More specifically, the inventionrelates to disposable, pre-calibrated, pre-validated optical sensors formonitoring biopharmaceutical solutions contained in enclosed spaces suchas single-use purification platforms and disposable bioreactors.

BACKGROUND OF THE INVENTION

Biopharmaceutical as well as clinical production facilities increasinglyemploy single-use containers including pre-sterilized, single-use,plastic tubing and collapsible plastic bags for solution storage andbioreactor applications. In addition, the downstream processing andpurification of bioreactor solutions is increasingly achieved withsingle-use, unit-operational platforms designed for the asepticpurification of solutions by normal flow filtration (NFF), tangentialflow filtration (TFF), chromatography and bioreactor applications.

Single-use platforms for downstream biopharmaceutical purificationtypically consist of an integrated assembly of filter elements orcolumns, flexible tubing, plastic connectors and solution storage bags,segments of peristaltic pump tubing as well as integrated sensors. Suchassemblies are designed and pre-assembled for a specific purificationprocess. Special, integral plastic connectors provide aseptic hook-up toexternal, single-use bioreactors and/or buffer solutions. In the finalconfiguration, all elements of the purification platform are assembled,pre-sterilized by gamma-irradiation. Dedicated peristaltic pumps areused to aseptically propel the process solution and buffers through thepurification tube manifold.

Pre-sterilized, single-use bag manifolds such as those used inbio-pharmaceutical production (see for example U.S. Pat. No. 6,712,963)lack the ability to monitor and validate important, analytical solutionparameters during the processing of biopharmaceutical solutions. The useof such bag manifolds, for example, in preparative chromatography ortangential flow filtration (TFF) or fluid transfer generally, isseverely limited by the general lack of pre-sterilized, pre-calibrated,pre-validated in-line sensors and detectors.

In-line, flow through-type sensors and detectors are well known inindustry and are extensively used in analytical laboratories, pilotplants and production facilities. Prior art in-line sensors anddetectors are difficult to sterilize, require in-field calibration andvalidation by an experienced operator before use, and are veryexpensive, often costing thousands of dollars. Consequently, prior artsensors and detectors are not suited for a single-use sensorapplication.

The need for pre-calibrated sensors arises from the fact that sensorcalibration after sterilization of the sensor-manifold assembly is notpossible without danger of re-contamination. On the other hand, sensorinsertion into a pre-sterilized manifold just prior to use is alsoproblematic since it would require the maintenance of a carefullycontrolled aseptic environment during on-site sensor calibration,sterilization and sensor insertion process. Breakdown of asepticconditions could result in serious process contamination and give riseto unacceptable economic losses.

In-line sensors for use in bioprocessing applications must be designedto satisfy several additional requirements. For example, they must meetgovernment regulations regarding device traceability and validation. Inaddition, in-line sensors must meet the application requirements foraccuracy and precision. These requirements present extra challenges andpose unique problems when the in-line sensor is to be disposable andsuitable for single use as desired. Furthermore, single-use sensors mustmeet economic requirements, i.e. sensors must be low cost, easy toreplace with negligible disposal expense.

Meeting sensor sterilization requirements represents another verysignificant sensor design challenge. This is especially the case, whenthe sensor is intended for single-use bag manifold applications such asthose described in the U.S. Pat. Nos. 6,712,963, 7,052,603 and 7,410,587and U.S. Patent Application Publication No. 2006/0118472 (all of whichare incorporated herein by reference).

In order to maintain a high quality of purification to a given set ofspecifications, pre-calibrated, single-use in-situ sensors are used formonitoring temperature, pressure, conductivity, and other solutionparameters. Such in-line (in-situ) sensors must be designed to withstandthe conditions of gamma-irradiation (˜35 kGy) and/or steam (˜123° C.)sterilization. The sensor may also endure sanitizing by ethylene oxidegas, electron-beam irradiation or a sodium hydroxide solution.

For many single-use sensor applications, e.g. for bag manifolds, thepreferred sterilization method by the industry is by gamma orelectron-beam irradiation. The main advantage of gamma and electron-beamirradiation lies in that the entire, pre-assembled manifold, includingbags, tubing, connectors and sensors, can be first sealed in a shippingbag and then exposed to sterilizing radiation or electron-beambombardment. The entire manifold assembly within the shipping bagremains sterile for a rated period, unless the shipping bag is comprisedduring shipment or storage.

For device/performance traceability, pre-calibrated sensors must containelectronically accessible sensor ID, sensor-specific calibration dataand lot-specific sensor performance data. This can be accomplished withintegration of a non-volatile, gamma-stable memory device into eachsensor. Sensor specific calibration information and ID number are storedin the memory device after successful factory calibration of the sensor.In addition, the calibration date stamp as well as lot-specific sensorperformance data is useful information stored in the non-volatilememory. In addition, the device must have sufficient memory capacity tostore relevant sensor data during processing for post-production reviewand analysis. See U.S. Pat. No. 7,857,506 and No. 7,788,047 (which areincorporated herein by reference).

SUMMARY OF THE INVENTION

The present invention applies to the monitoring of turbidity and othersolution parameters important in biopharmaceutical processing andpurification of biologically derived molecules, including proteins,living cells and systems incorporating same. The invention is alsorelevant to the production of personal medicine, i.e. the clinicalprocessing and purification of patient-specific molecules includingexpansion and purification of autologous cells and protein.Specifically, the invention addresses the process analytical challengesthat arise from the need for in-situ solution monitoring inpre-sterilized, single-use bioreactors (SUB), single-use,unit-operational purification platforms and plastic tube manifolds suchas those disclosed in U.S. Pat. Nos. 6,712,963, 7,052,603 and 7,410,587and U.S. Patent Application Publication No. 2006/0018472.

The disclosed invention provides optical sensor technology that meetsall of the industry's requirements, including those identified herein.The invention provides optical methods and devices for quantitativemeasurements of solution turbidity and other optical density (OD)measurements such as those typically required in normal flow filtration(NFF), tangential flow filtration (TFF), chromatography and bioreactorapplications.

The subject device or system comprises a reusable sensor assembly and adisposable optical bench or inset optical component. The disposableoptical component can be molded and imbedded in a disposable flowcell orstorage bag. The optical bench has a fluid-contacting surface side and adetector surface side. On the fluid-contacting surface side, the opticalbench is designed to set within the flowcell or bag and includes one ormore appropriately shaped reflectors and includes a detector window(e.g., a scattered light window). The reflectors are optically isolated(or otherwise isolated) from the detector window, which is locatedadjacent to one reflector or located between two or more reflectors. Theoptical bench securely mates to the sensor assembly on the detectorsurface side of the optical bench or bench module.

The sensor assembly typically includes electro-optical componentsmounted onto a flat sensor printed circuit board contained within ahousing. Electro-optical components of the sensor assembly typicallyinclude circuitry, a high-intensity light source (such as a laser orLED), an aperture disk, a micro lens, an optical alignment bezel, areference detector, and a photo detector. Multiples of such componentscan be provided, such as multiple photo detectors. The expensiveelectro-optical components and associated electronics are designed as aseparate, detachable module sized and structured for repeated, long-termuse.

The sensor assembly can be readily connected and secured to apre-sterilized, gamma-irradiated system via the optical bench or benchmodule sealingly connected to a flowcell or storage bag withoutcompromising system sterility. After the bench module and the sensorassembly are mated such as at respective docking ports, the opticalsensor may be operated to measure the solution parameter of interest,such as turbidity, particle size, pH and/or protein concentration.

The sensor operates by generating a high-intensity energy beam in thevisible, near-visible or IR wavelengths. In an illustrated embodiment,the energy beam is focused by a micro-lens and passes through theaperture disk. The energy beam then passes though the detector side ofthe optical bench. The energy beam is reflected off a reflector andpasses out of the fluid-contacting side of the optical bench and throughthe fluid. As the energy beam encounters solution particulate within thefluid, a portion of the photons of light are scattered by theparticulate. The remaining photons may pass to a reference detector. Inan embodiment, these remaining photons pass back through thefluid-contacting side of optical bench, reflect off a reflector and aremeasured by the reference detector. A portion of the photons scatteredby the particulate travel through the transparent scattered light windowof the optical bench and are measured by one or more photo detectors. Acomparison and calculation of the value measured by the referencedetector and the values measured by the photo detectors yieldsinformation on the solution parameter of interest, such as the turbidityof the fluid.

The optical bench or bench module may have several differentconfigurations. Same may have a single or unitary construction,comprising of opposing, facing reflectors on the fluid-contacting sideseparated by a transparent detection window. On the detector side of theoptical bench, the optical bench may have angled or non-perpendicularbeam entrance window and optical channels or optical channels which aregenerally perpendicular to the transparent window.

Another configuration of the optical bench comprises separatecomponents. In such a configuration, the opposing, facing reflectors andtransparent detection window of the optical bench are each separatecomponents sealed to the flowcell, bioreactor bag, container or storagebag.

The optical bench or bench module may also comprise a single reflectorand a transparent detection window. In this configuration, the opticalbench does not include a return reflector. This design configuration isparticularly useful for measuring low turbidity.

The disposable flowcell or storage bag may include a printed circuitboard (PCB) that includes a gamma-stable memory circuit or device. Thememory circuit or device is capable of storing information such ascalibration data, serial number, lot number and/or lot specificperformance data associate with the disposable flowcell or storage bag.The memory device may also include an “out-of-box” performance variancevalue, which “out-of-box” value is a statistically derived performancevariance that represents the maximum measurement error for thatdisposable flowcell or storage bag within a defined confidence limit.

In addition, the sensor assembly may also include a printed circuitboard (PCB) that includes a gamma-stable memory circuit or device. Thememory circuit or device on the sensor assembly is capable of storingidentification information such as calibration data, serial number, lotnumber and/or lot specific performance data associate with the sensorassembly. The memory device may also include an “out-of-box” performancevariance value. This “out-of-box” value is a statistically derivedperformance variance that represents the maximum measurement error forthat sensor assembly within a defined confidence limit.

It is a general aspect or object of one or more embodiments of thepresent invention to provide an optical sensor.

Another aspect or object of one or more embodiments of the presentinvention is to provide a disposable component of the sensor suitablefor one-time use, which may be integrated with other disposableequipment, including bag manifolds, employed in the separation andpurification of fluids that are suitable for single-use applications.

A further aspect or object of one or more embodiments of the presentinvention is to provide an optical bench or optical inset componentarrangement for a modular system of sensing and measuring.

An aspect or object of one or more embodiments of the present inventionis to reduce the cost associated with the construction of disposableoptical sensors.

Another aspect or object of one or more embodiments of the presentinvention is to provide a disposable component and a sensor assemblyeach having means to store sensor-specific information, which is notaffected by sterilization techniques.

These and other objects, aspects, features, improvements and advantagesof the present invention will be clearly understood through aconsideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a disposable flowcelland a reusable sensor assembly.

FIG. 2 is an exploded perspective view illustration of the disposableflowcell and a reusable sensor assembly illustrated in FIG. 1.

FIG. 3 is a longitudinal cross-section view of one embodiment ofturbidity sensor with the flowcell assembly mated to a reusable sensorassembly.

FIG. 3A is an enlarged schematic view of the optical bench portion ofFIG. 3.

FIG. 4 is a longitudinal cross-section view of another embodiment ofturbidity sensor with the flowcell assembly mated to a reusable sensorassembly.

FIG. 4A is an enlarged schematic view of the optical bench portion ofFIG. 4.

FIG. 5 is a longitudinal cross-section view of another embodiment ofturbidity sensor with the flowcell assembly mated to a reusable sensorassembly.

FIG. 6 is a longitudinal cross-section view of a disposable bioreactorbag with a glued-in optical bench mated to a sensor assembly.

FIG. 7 is a graph of the ratiometric laser pulse turbidity response inthe 1 to 1000 NTU range.

FIG. 8 is a graph of the ratiometric laser pulse turbidity response inthe 0.1 to 10 NTU range.

FIG. 9 is a flowchart of the steps to calibrate a disposable turbiditysensor.

FIG. 10 is a flowchart of the steps to utilize a disposable turbiditysensor to determine the turbidity of a fluid.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific details disclosed herein are not to beinterpreted as limiting, but merely as a basis for the claims and as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention in virtually any appropriate manner.

A system designed to measure the turbidity of fluids in a closed fluidsystem by using a pre-calibrated disposable flowcell assembly 100containing an in-line optical bench and a sensor assembly 120 is shownin FIG. 1. The flowcell assembly is generally designated as 100. Theassembly 100 is designed to be integrable with a fluid circuit and to bedisposable. Contained with the flowcell assembly 100 is a short tubularfluid conduit 102 surrounded by a cover 104.

The fluid conduit 102 is molded and designed for passing a fluid throughits interior at a particular manifold flow rate range. It is intended tobe connected to a fluid circuit or processing system, though it may haveother uses. The tubing material of the fluid conduit 102 should besuitable for engaging and containing the fluid being handled, such asvaluable proteins, protein systems, cells, cell systems, biotechnicalcompositions or pharmaceutical solutions. The fluid conduit 102 hasmolded-in fluid-tight connections such as inlet 106 at a first end andoutlet 108 at a second end, which may consist of Luer, Barb, Triclover,or any connection method suitable to sealingly connect the fluid conduit102 to a fluid-containing component in a processing system or fluidcircuit such as those identified herein.

The underside of the flowcell assembly 100 mates to the reusable sensorassembly 120. The reusable sensor assembly 120 includes barbed bolts 122and 124, which when mated to the flowcell assembly 100, are insertedthrough its underside. The illustrated flowcell assembly 100 is thensecured by means of a rotating, locking action by which the barbed boltsreleasably engage to connect together the flowcell assembly and thereusable sensor assembly.

The reusable sensor assembly 120 is connectable to a readout device,computer, processor, sensor monitor, or user interface via connectionport 126. The reusable sensor assembly 120 includes sensor-specificcircuitry, which also includes a gamma-stable, non-volatile memorydevice, chip or an EEPROM. The circuitry and non-volatile memory areaccessible through the connection port 126. The non-volatile memory chipor EEPROM is used to store sensor-specific information. The non-volatilememory device associated with the reusable sensor assembly 120 storesthe subassembly identity information, calibration values, calibrationfactors and calibration date as well as the performance characteristicsof the sensor assembly 120. This information can be called up, displayedand printed out, on demand, by a readout device, processor, computer,sensor monitor, or user interface connected to the connection port 126.

The sensor assembly 120 also connects to a second non-volatile memorydevice, chip or EEPROM located within the flowcell assembly 100. Whenthe flowcell assembly 100 and sensor assembly 120 are mated, the secondvolatile memory device is connected to sensor circuitry via electricalcontacts 128. The second non-volatile memory device contains data, suchas calibration values, calibration factors, performance characteristics,flowcell identification information and factory calibration data. Whenthe flow cell is engaged, i.e. connected to the sensor assembly 120, thestored flowcell data is accessible through the circuitry of the sensorassembly 120 and is downloadable by any connected readout device,computer, sensor monitor, or user interface via connection port 126.Barcode, RFID or wireless technology also could be utilized forinformation handling.

The sensor assembly 120 includes apertures that are sealed against fluidtransfer while allowing passage of electromagnetic radiationtherethrough, such as the illustrated windows 130 and 132. When thesensor assembly 120 is mated to the flowcell 100 such as by respectivedocking ports, the illustrated aperture windows align with apertureplates located on the underside of the flowcell assembly 100. A energybeam source, such as LED, laser or other source of electromagneticradiation is positioned directly below aperture window 130, within thesensor assembly 120.

Positioned below illustrated aperture window 132 is a reference photodetector. The reference photo detector is sensitive to theelectromagnetic radiation produced by the energy beam source of thisembodiment. Located between the aperture windows 130 and 132 is onoptical window 134 in this embodiment. As shown in FIG. 2, a photodetector resides underneath the optical window 134.

FIG. 2 shows exploded views of the disposable flowcell assembly 100 andthe reusable sensor assembly 120. The flowcell assembly 100 has ahousing comprised of a cover 210 which sealingly and securely mates tothe flowcell base 220. Connected to the flowcell base of this embodimentis a fluid conduit tube 102, with molded-in fluid-tight connections 106and 108. The inner wall surfaces of the fluid conduit tube 102 are partof the sensor solution interface. For optimal sensor response, the innerwall surfaces of the flow-through sensor can have a mirror-like,reflective surface finish. The fluid conduit tube 102 also includesopenings for the optical components.

The optical components illustrated in this embodiment comprise tworeflective components that fold or change the direction of anelectromagnetic radiation beam. These can be considered to be foldmirrors 222 and 224 that can be molded members with appropriately shapedreflectors. Another optical component of this embodiment is a scatteredlight detection window 226. The optical components can be molded fromoptically transparent plastic. The optical components typically aremechanically integrated (e.g. glued) into the fluid conduit tube 102,usually also a plastic or polymer. Mechanically integrating the opticalcomponents into the liquid-carrying sensor tube provides a physicalseparation between the fluid and the active electro-optical sensorcomponents and maintains a hermetically sealed sensor-solutioninterface. When mechanically integrated, the optical components areoptically isolated and surrounded by opaque material, such as molded orextruded polymeric material, in order to minimize undesirable backgroundlight scattering.

Two reflective components or fold mirrors are shown, one being anoriginating fold mirror 222 and the other a receiving fold mirror 224.Each fold mirror has a reflective surface, a fluid-contacting surface,and a detector surface side. The reflective surface can be made of asuitable material such as gold, aluminum, silver, nickel or alloys orcombinations thereof, or polymers that contain such materials or areotherwise reflective. The fold mirrors 222 and 224 and the scatteredlight window 226 form an optical bench or bench module in its mostelemental form. When integrated with the fluid conduit 102, the foldmirrors 222 and 224 as well as one side of the scattered light window226 are oriented toward the inside of the tube 102 and are in contactwith the solution contained within the tube 102. The scattered lightwindow has ridge 227, which is in direct contact with the interior ofthe fluid conduit 102 when the window is integrated.

The scattered light window 226 and the fold mirrors arenon-circumferential (i.e. they do not extend around the fullcircumference of the fluid conduit 102). Typically these optical benchcomponents, and usually the entirety of the optical bench, do not extendgreater than half of the circumference of the fluid container (conduitin this embodiment). For example, in FIG. 3, the optical bench extendsfor about one third of the circumference of the conduit.

In this embodiment, the fold mirrors 222 and 224 and scattered lightdetector window 226 are integrated into the plastic fluid conduit tube102 in an aligned, collinear, longitudinal orientation. The longitudinalorientation the fold mirrors 222 and 224 and the separation ofelectro-optical components (light source and detectors) contained withinsensor assembly 120 results in an optical path that is independent ofany fluid conduit dimensions. This arrangement allows for an easyphysical separation of light source and detectors and theliquid-carrying conduit. Thus, dimensional scale-up of fluid conduits isreadily achieved without changing the optical path dimensions. Forexample, the same dimensioned optical bench can be incorporated into a⅛″ diameter or a 1.0″ diameter fluid conduit or into the walls of a 20liter bioreactor bag while obtaining the same signal, such as aturbidity signal, for a given solution.

Aperture plates 228 and 230 are located in the flowcell assembly 100sealed below the respective fold mirrors 222 and 224. The apertureplates 228 and 230 optically isolate the fold mirrors 222 and 224. Theaperture plates 228 and 230 each contain a minute aperture 232 and 234to allow the energy beam, laser, or the electromagnetic radiationgenerated by the source within the sensor assembly, to pass. When theflowcell assembly 100 and the sensor assembly 120 are mated, aperture232 located in the aperture plate 228 is positioned above and in opticalalignment with the energy beam source contained within the sensorassembly 120. Similarly, aperture 234 in aperture plate 230 ispositioned above the reference photo detector, when the flowcellassembly 100 and sensor assembly 120 are mated.

As stated above, the flowcell assembly 100 also includes a memorydevice, such as a gamma-stable, non-volatile memory device, a chip or anEEPROM, for example, which memory device is connected to a printedcircuit board 236. The printed circuit board 236 is located within theflowcell assembly 120. The non-volatile memory device on the printedcircuit board 236 contains data associated with the single-use,disposable flowcell 100, as stated above.

When the flowcell assembly 120 is engaged with, typically by beingsealed to, the sensor assembly 120, the printed circuit board 236electrically connects to the electrical contacts 128. As stated above,when the flowcell is connected to the sensor assembly 120, the storedflowcell data is accessible through the circuitry of the sensor assembly120 and is downloadable by any connected (hardwire or wireless) readoutdevice, processor, computer, sensor monitor, or user interface viaconnection port 126.

When the flowcell assembly 100 and the sensor assembly 120 are mated,aperture plates 228 and 230 optically align with the aperture windows130 and 132, and the scattered light detector window 226 opticallyaligns with the detector window 134. The aperture windows 130 and 132and detector window 134 are located on top cover 238 of the sensorassembly 120.

The connection port 126 is electrically connected to the printed circuitboard and the components thereon. A energy beam source 244, such as LED,laser or other source of electromagnetic radiation is surface mountedonto the flat printed circuit board 242. In one embodiment, a laserdiode which produces a light with the wavelength of approximately 660 nmis utilized. The operational pulse frequency of a laser diode rangesfrom 1 Hz to 10 kHz. The laser pulse width may range from 10 seconds to1 microsecond, and the laser pulse height in terms of current rangesfrom 10 milliampere to 1.0 ampere. In the embodiment which utilizes thelaser diode at 660 nm, 180 Hz is the preferred pulse frequency, 10milliseconds is the preferred pulse width, and 0.5 ampere is thepreferred pulse height current. In another embodiment the energy beamsource generates ultraviolet light with a wavelength of approximately280 nm. In this alternative embodiment, the energy beam source 244 is anultraviolet diode with a hemispherical lens arrangement such as thosesold by Sensor Electronic Technology Inc. (UVTOP280, TO39FW). Thepreferred ultraviolet diode has a high optical power output in the 400to 800 micro-Watts (uW) range and a narrow viewing angle, preferably<10°.

A photo detector 246 and a reference detector 248 are also surfacemounted onto the flat printed circuit board 242. The scattered lightphoto diode detector 246 and reference diode detector 248 may bearranged collinearly with the light source 244, and same are sensitiveto and can measure the light or electromagnetic radiation generated bythe energy beam source 244. The surfaces of the scattered light photodiode detector 246 and reference diode detector 248 are aligned at anangle of approximately 90 degrees from the energy beam originating fromthe energy beam source 242.

All electro-optical components are surface-mounted onto a flat sensorprinted circuit board 242. In this embodiment, the component side of theprinted circuit board 242 is fastened to a molded plastic enclosure topcover 238, the molded plastic enclosure top cover 238 with separatecavities accommodating the energy beam source 244 with a collimatinglens as well as scattered light photo diode detectors 246 and referencephoto diode detector 248. The top cover 238 attaches to the bottomsealing cover 240, securing the printed circuit board 242 safely betweenthe two.

The sensor circuitry within the printed circuit board 242 or within aconnectable readout device, processor, computer, user interface, etc.provides a means of automatically interrupting the laser operation whenthe attached flowcell assembly 100 is disengaged from the sensorassembly 120. This is an important safety feature to prevent eyeinjuries, for example, during removal of the disposable flowcell 100.

FIG. 3 shows longitudinal cross-sectional view of a flowcell assemblywith disposable fluid conduit tube 302 mated to a reusable sensorassembly 304. The disposable fluid conduit tube 302 has an interiorsurface 303 and an exterior surface 305. The interior surface may have amirrored or reflective coating.

The reusable sensor assembly has a housing 306 which protects theprinted circuit board 308. An energy beam source 310, which may be alaser diode, LED, or other source of electromagnetic radiation issurface-mounted onto the flat printed circuit board 308. One or morephoto diode detectors 312 a, 312 b, and 312 c and a reference photodiode detector 314 are also surface mounted onto the flat printedcircuit board 308. The housing 310 includes a cavity formed by walls 316a and 316 b, which optically isolate the energy beam source 310 from theother components. Similarly, walls 318 a and 318 b optically isolate thephoto diode reference detector 314 from the other components.

The housing may also include cavities 320 a and 320 b which accommodatefold mirrors 322 and 324. The tabs 326 and 328 located on the undersideof the fold mirrors 322 and 324 fit into these cavities 320 a and 320 b.The tabs 326 and 328 properly align the disposable fluid conduit withthe reusable sensor assembly.

The fold mirrors 322 and 324 and the scattered light detector window 330may be manufactured from any material suitable for the opticaltransmission of electromagnetic radiation and which may withstandsterilization. The preferred material is TOPAS®, a cyclic olefincopolymer, with refractive index of 1.53. The polymer is opticallytransparent from UV to the near IR wavelength range. The use of TOPAS®polymer allows low-cost mass-production and easy integration intodisposable, plastic sensor tubes, bags or plastic hard-shell containers.

The fold mirrors 322 and 324 and the optical detector window 330 areintegrated into their respective recesses or cavities in the disposablefluid conduit tube 302. The cavities that accommodate the optical foldmirrors 322 and 324 and detector window 330 are molded into thedisposable sensor tube and provide mechanical alignment with respect tothe optic-electronic detector components. The fold mirrors 322 and 324and the scattered light detector window 330 may be glued into recessesin the disposable fluid conduit tube 302. Gluing the optical componentsinto the liquid-carrying sensor tube provides a physical separationbetween the fluid and the active electro-optical sensor components andmaintains a hermetically sealed sensor-solution interface. The precisionof the mechanical alignment of the fold mirrors 322 and 324 and theoptical detector window 330 is of critical importance for anyanalytical, light-based measurements, for example transmittance,absorbance, reflectance, light scattering or fluorescence.

In this embodiment, the fold mirrors 322 and 324 are separated andoptically isolated from the scattered light detector window 330 by lightblocks 332 and 334. Light blocks 332 and 334 are opaque plasticmaterial, which prevents the transmission of electromagnetic radiation.

A beam 336 of electromagnetic radiation is generated by the beam source310. The energy beam 336 may be further focused, such as by a lens 338,before passing though an aperture disk or aperture plate 340. Theaperture disk 340 includes a small aperture through which the beam 336passes, which aperture limits the diameter of the beam 336 and, thus,limits the amount of light or other energy beam which passes. Theaperture disk 340 provides a consistent diameter beam 336 to providecontrol in that beam sources within a production lot may slightlydiffer. The energy beam source 310, lens 338, and aperture disk 340 areheld in place and aligned by an optical alignment bezel 342 in thisillustrated embodiment.

The beam 336 generated by energy beam source 310 is oriented vertically.The beam 336, after passing though the lens 338 and aperture disk 340,enters through receiving window 344 of fold mirror 322 and is reflectedoff the mirror-coated reflective surface 346. In order to avoidrefractive light or energy beam losses and undesired scattering, theembodiment shown in FIG. 3 relies on two, opposing fold mirrors 322 and324 with internal, mirror-coated reflector surfaces 346 and 350,respectively. The mirror-coating 348 is a material sufficient to reflectelectromagnetic radiation, such as gold. The fold mirrors 322 and 324extend within the fluid conduit 302. As a result, the angled reflectivesurfaces 346 and 350 of the fold mirrors 322 and 324 (and the opticalbench) are located within the interior of the fluid conduit tube 302 andextend toward the longitudinal axis of the fluid conduit 302.

The optical light path is further illustrated in FIG. 3A. As shown inFIG. 3A, angle “β” (beta) between the vertical energy beam 336 generatedby the vertically positioned energy beam source 310 and the normal(illustrated at 364) of the reflector surface is less than or equal to acritical angle, typically 45 degrees. The energy beam 336 is reflectedoff the internal, mirror-coated reflective surface 346 and travels at anapproximately 90 degree angle from its originating vector. The angle mayvary so as to account for the refractive indexes of the material used(including of the windows) and the fluid contained within the fluidconduit 302. The energy beam 336 exits the fold mirror through theemitting reflector window 352 on the fluid-contacting side of the foldmirror 322.

On the fluid-contacting side of the fold mirrors, the reflected laserbeam transverses a path generally parallel to an optically transparentscattered light window 330. The scattered light window is locatedbetween and below the emitting reflector window 352 and the receivingreflector window 354 of fold mirror 322 and 324, respectively. On thefluid-contacting surface of the fold mirrors, the emitting reflectorwindow 352 radiates a high-intensity, collimated energy beam 336parallel to the inside (longitudinal) fluid conduit tube 302 surface andparallel to the scattered light window 330. In the case of flow throughsensor designs, the inner wall surfaces are part of the sensor solutioninterface.

On the fluid-contacting side of the fold mirrors 322 and 324, theemitting reflector window 352 as well as the receiving reflector window354 oppose each other and are oriented at approximately 90 degrees withrespect to the energy beam 336 as the originating energy beam 336transverses through the fluid conduit 302. The orientation angle mayvary given the respective refractive indices of the fluid and of thefold mirrors 322 and 324.

As the energy beam 336 travels though the fluid contained within thefluid conduit tube 302, it may strike and be scattered by particulatematter within the fluid. This scattered energy beam or light 356(represented by arrows) may then pass through the scattered lightdetector window 330 and be detected and measured by one or more photodetectors 312 a, 312 b, and 312 c.

That portion of beam 336 that travels unabated, unimpeded, orun-reflected through the fluid passes through the receiving reflectorwindow 354 of fold mirror 324. The energy beam 336 is reflectedapproximately 90 degrees downward by the internal, mirror-coatedreflector surface 350, which as an acute angle with respect to theenergy beam path. The mirror-coated reflector surface 350 has a surfacenormal to it, as illustrated at 366 in FIG. 3A. The angle “δ” (delta)between the energy beam 336 and the normal 366 is less than or equal toa critical angle, typically 45 degrees. The mirror-coating 358 whichcreates mirror-coated reflector surface 350 is a material sufficient toreflect electromagnetic radiation, such as gold.

The reflected beam 336 travels downward through the exiting window 360of the fold mirror 324. The remaining portion of the beam 336 isdirected towards reference photo detector 314. The reference photodetector 314 monitors the transmitted laser light or energy beam andacts as a reference detector, i.e. it detects and measures the intensityof the beam 336 that traveled unabated through the fluid conduit tube302.

The analytical signal, derived from the detected scattered energy beamsor light 356 (represented by arrows) of suspended solution particulates,is generated within the space defined by the diameter of the beam 336 asit transverses the fluid conduit 302 and the distance between the two,opposing emitting reflector window 352 and receiving reflector window354. The embodiment shown in FIG. 3 also allows monitoring the outputsof either scattered energy beam or light detectors 312 a, 312 b, and 312c or the output of the reference photo detector 314 or the signal ratioof (scattered light detector/reference detector). The ratio-metricapproach provides a means for removing the effects of solution colorand/or protein adsorption on any of the windows of the optical bench(e.g. the scatter light window 330). Monitoring of the output of one ormore of the scattered light detectors 312 a, 312 b, and 312 c and theoutput of the reference photo detector 314 cancels any interferencepresent in the measurement, as it is understood that the scattered lightdetectors 312 a, 312 b, and 312 c and reference photo detector 314 areequally affected.

Sensor circuitry, located on the printed circuit board 308, or in aconnectable readout device, processor, computer, user interface, etc.allows measurement of photo detector dark currents between laser pulses.The photo detector current measured during the laser pulse minus thephoto detector dark current measured between pulses constitutes theanalytical turbidity signal.

The longitudinal fold mirror orientation within the fluid conduit tube302 and separation of electro-optical components by the energy beamsource and photo detectors generates an optical path that is independentof any dimensions of the fluid conduit tube 302. This arrangement allowsfor an easy physical separation of energy beam source and detectors onone hand and the liquid-carrying conduit on the other hand. Thus,scale-up of conduit dimensions are readily achieved without changing theoptical path dimensions. The same dimensioned optical bench can beincorporated into differently sized systems. For example, the sameoptical bench dimensions can be used with a range of fluid containersizes, such as a ⅛″ diameter, a 1.0″ diameter (or intermediate orother-sized diameter) liquid conduit or into the walls of a bioreactorbag, while obtaining the same signal for a given calibration solution,such as a turbidity calibration solution.

The optical path of the energy beam 336 of this embodiment originates atthe energy beam source 310. The optical beam flows in a straight path orline through a lens 338 and through an aperture disk 340, and entersthrough the first surface of a first member of the optical bench orbench module, the receiving window 344 of fold mirror 322.

The optical path is then reflected off a second surface, the reflectivesurface 346 or the first member, of the optical bench. This secondsurface, the reflective surface 346, has an acute angle relative to thisfirst surface, the receiving window 344. The optical path exits out ofthe first fold mirror 322 through a third surface of the first member,emitting reflector window 352. The scattered light window 330 is locatedbelow reflective surfaces 346 and 356. As a result, the optical pathtravels through the fluid conduit tube 302, above the upper surface 362of the scatter light window 330. In this illustrated embodiment, theoptical path is generally parallel to the upper surface of the scatterlight window 330.

The optical path in this embodiment continues to a second member,through its fourth surface, receiving reflector window 354 of the secondfold mirror 324. The third surface and this fourth surface substantiallyoppose each other. A fifth surface of the second member, reflectivesurface 358, reflects the optical path downward through a sixth surfaceof the second member, the exiting window 360 of the fold mirror 324.This fifth surface, the reflective surface 356, has an acute anglerelative to this sixth surface, the exiting window 360. The optical pathconcludes at a photo detector 314. The first, third, fourth, and sixthsurfaces and said upper surface of the scattered light window 330 areoptically transparent allowing for the transmission of electromagneticradiation.

All critical dimensions of the optical path of the energy beam 336 arestable and fixed. Collimated energy beam 336 traces are well defined andcan be reproducibly generated. This design feature allows sensorcalibration and scalability. For example, for a given turbiditysolution, the same optical sensor response is obtained regardless of thesensor tube diameter or the container size.

FIG. 4 shows another embodiment of the present invention. The embodimentshown in FIG. 4 demonstrates modifications to the embodiment presentedin FIG. 3. Some or all modifications may be practiced. These includethat the optical bench 402 may be a unitary piece. Also, the originatingvector of energy beam 404 may be angled rather than generallyperpendicular with respect to the conduit tube and/or scattered lightwindow, with the result that the reflection angle is greater than 90° orobtuse. In another variation, the reflective surfaces 406 and 408 of theoptical bench are non-mirrored surfaces, i.e. have no mirrored coating.

The optical bench 402 as shown in FIG. 4 is a unitary piece withoutseparate components. Such an optical bench may include in its unitaryconstruction light blocks to prevent the transmission of light throughunintended areas of the optical bench 402. This optical bench embodimentincludes entrance window 412, an emitting window 414, a receiving window416, and an exit window 418. The emitting window 414 and receivingwindow 416 are located on the fluid-contacting side of the opticalbench. The emitting window 414 and receiving window 416 are opposing,facing windows. Located between the emitting window 414 and thereceiving window 416 is the scattered light window 420. The opticalbench 402 may be made of any material which permits the transmission ofelectromagnetic radiation, such as a beam of infra-red (IR) orultra-violet (UV) light.

Optical bench 402 of this embodiment is integrated with a disposablefluid conduit tube 422. The fluid conduit tube 402 is shown in FIG. 4attached to the reusable sensor assembly 424. Reusable sensor assembly424 includes a printed circuit board 426 on which electro-opticalcomponents are mounted. A energy beam source 428, which may be a laserdiode, LED, or other source of electromagnetic radiation, is mountedonto the flat printed circuit board 426. The energy beam source 428 maybe mounted at an angle other than 90° such that the energy beam 404originates at an angle other than 90° with respect to the printedcircuit board. It is also contemplated that the energy beam 404 may beangled in this sense by means of a mirrored surface contained within thereusable sensor assembly 424.

Adjacent the energy beam source 428 is a lens 430. Located along theoptical path from the lens 430 is an aperture disk 432. The energy beamsource 428, lens 430 and aperture disk 432 are held in optical alignmentby an optical alignment bezel 434 or the like.

One or more scattered light photo diode detectors 436 a, 436 b, and 436c are mounted on the printed circuit board 426. A reference photo diodedetector 438 is also mounted to the printed circuit board 426. Thescattered light photo diode detectors 436 a, 436 b, and 436 c, referencephoto diode detector 438, and the energy beam source 428 are collinearlyarranged on the printed circuit board 426.

Optically opaque walls 440 and 442 of the sensor assembly 424 separatethe components. The scattered light photo diode detectors 436 a, 436 band 436 c are separated from the energy beam source 428 by opaque wall440. Likewise, the scattered light photo diode detectors 436 a, 436 band 436 c are separated from the reference photo diode detector 438 byopaque wall 442. The opaque walls insolate the components, especiallythe detectors, from unintended electromagnetic radiation.

The optical path of the energy beam 404 originates at the energy beamsource 428. The originating vector of the energy beam 404 is angled,though it is contemplated that the energy beam 404 may be “bent” angledvia a mirrored surface contained within the sensor assembly 424. Theenergy beam 404 travels though a focusing lens 430 and aperture disk432. The aperture disk 432 includes a small aperture which limits thediameter of the energy beam 404. The energy beam 404 enters the opticalbench through entrance window 412 and is reflected off the reflectivesurface 406.

The reflective surfaces 406 and 408 use the refractive properties of thematerial used from which the optic bench 402 is constructed and thefluid components contained with the fluid conduit tube 402 that reflectthe electromagnetic radiation. As shown in FIG. 4A, the angles “θ”(theta) and “φ” (phi) between the energy beam 404 and the normal 446 ofreflector surface 406 and the normal 448 of reflector surface 408 isgreater than or equal to a critical angle. The critical angle of thereflective surfaces 406 and 408 is defined by: αc=arcsin (n1/n2), wheren1 is index of refraction of the solution (1.33 for water) and n2 is theindex of refraction of the optical reflector material (1.53 for TOPAS®,COC). For example, a water-TOPAS® reflector interface, the criticalangle is approximately 57°. For any angle of “θ” and “φ” which isgreater than or equal to 57° the energy beam 404 is totally reflected atthe internal reflector surface 406 or 408. If the angle is less than 57°the energy beam is partially refracted through the internal reflectorsurface and constitutes an undesirable optical background scatter.

On the detector side of the optical arrangement, a beam entrance window412 is located approximately 90°, or normal to the optical axis of theenergy beam 404 that originates from the energy beam source 428 (i.e. alaser diode in this embodiment) and associated aperture of the aperturedisk 432. The optical beam axis intersects with the normal of theinternal reflector surface at an angle that is equal or larger than thecritical angle, αc.

The incident energy beam 404 is reflected from the internal reflectorsurface 406 making an angle “θ” (with respect to the normal 446 ofsloped reflector surface 404) that is defined by φ≧αc=arcsin (n1/n2), asdefined above. Once reflected, the energy beam 404 travels through theemitting window 414 located on the fluid-contacting side of the opticalbench 402. The energy beam 404 then travels through a fluid containedwithin the fluid conduit tube 422. As it travels through the fluid, theenergy beam 404 is scattered by particles in the fluid. This scatteredlight 440 (represented by arrows) may travel through the scattered lightwindow 420 of the optical bench 402. The scattered light 440 strikes andis measured by one or more of the scattered light photo detectors 436 a,436 b, and 436 c.

The portion of energy beam 404 that travels unabated, unimpeded, orun-reflected through the fluid passes through the receiving reflectorwindow 416. The energy beam 404 is then reflected by internal reflectorsurface 408 making an angle “φ” (with respect to the normal 448 ofsloped reflector surface 408) that is defined by θ=αc=arcsin (n1/n2), asdefined above. Once reflected, the energy beam travels through theexiting window 418 located on the detector side of the optical bench402. After exiting the inset optical component or optical bench 402, theenergy beam 404 strikes reference detector 438 and is measured there bythe reference detector 438.

The analytical signal, derived from the detected scattered light 444(represented by arrows) of suspended solution particulates, is generatedwithin the space defined by the diameter of the energy beam 404 as ittransverses the fluid conduit 422 and the distance between the two,opposing emitting reflector window 414 and receiving reflector window416. The embodiment shown in FIG. 4 also allows monitoring the outputsof either scattered light detectors 436 a, 436 b, and 436 c or theoutput of the reference photo detector 438 or the signal ratio of(scattered light detector/reference detector). The ratiometric approachprovides a means for removing the effects of solution color and/orprotein adsorption on any of the windows of the optical bench (e.g. thescatter light window 420).

FIG. 5 shows another embodiment of the present invention anddemonstrates possible modifications to the embodiments presented in FIG.3 and FIG. 4. As shown in FIG. 5, in this embodiment, the optical benchhas only one internal reflector. The optical bench does not include areceiving window, a second internal reflector, or an exit window.Additionally, the sensor assembly 506 of this embodiment does notnecessarily include a reference detector. It is contemplated that thesensor assemblies as shown in the embodiments of FIG. 3 and FIG. 4 maybe connected to the optical bench in FIG. 5; however, the referencedetector is turned off or is not utilized when such a connection ismade. The embodiment having a single internal reflector, as demonstratedin FIG. 5, is particularly useful for very low NTU turbiditymeasurements.

The optical bench in FIG. 5 comprises a fold mirror 502 and a scatterlight detector window 504 integrated within a disposable fluid conduittube 506. The fold mirror 502 and the scattered light window 504 aremade of any material which permits the transmission of electromagneticradiation, such as a beam of light.

Located between the fold mirror 502 and the scattered light window 504is a light block 508. The light block 508 is made of opaque material andprevents the inadvertent transmission of electromagnetic radiation. Asecond light block 510 may be located on the opposite side of thescattered light window 504. The second light block may be made of opaquematerial and prevents the inadvertent transmission of electromagneticradiation through to the components of the reusable sensor assembly 512.

In this embodiment, the fold mirror 502 includes an internal,mirror-coated reflector surface 514. The mirror-coating material 516 isany material that can reflect electromagnetic radiation, such as thosediscussed herein. A non-mirror-coated reflector surface may also be usedas described above. The fold mirror 502 also includes an entrance window518 and an emitting window 520.

The disposable fluid conduit tube 506 is removably attached to thereusable sensor assembly 512. The reusable sensor assembly includes aprinted circuit board 520. Mounted on the circuit board are one or morescattered light photo diode detectors 522 a, 522 b, and 522 c and aenergy beam source 524, which may be a laser diode, LED, or other sourceof electromagnetic radiation. The scattered light photo diode detectors522 a, 522 b, and 522 c and a energy beam source 424 may be collinearlyarranged on the printed circuit board.

The energy beam source 524 generates a energy beam 526 ofelectromagnetic radiation. The energy beam 526 travels through a lens528 which focuses the energy beam 526. Thereafter, the energy beam 526passes through an aperture disk 528. The aperture disk 528 has a smallaperture which limits the diameter of the energy beam 526. The energybeam 526 then pass through the entrance window 518 of fold mirror 502.After entering the fold mirror 502, the energy beam is reflected off ofthe internal, mirror-coated reflector surface 514. The energy beam thenpasses out of the fold mirror 502, through the emitting window 520 andinto the fluid contained within the fluid conduit tube 506. The energybeam 506 may encounter suspended particles in the fluid, which createsscattered energy beams 530 (represented by arrows). The energy beam 506continues indefinitely through the fluid conduit tube.

The scattered energy beams 530 may pass through the scattered lightwindow 504 of the optical bench of this embodiment. Thereafter, thescattered energy beams 530 strike and are measured by one or more of thescattered light photo detectors 522 a, 522 b and 522 c.

FIG. 6 shows an embodiment having optical bench or optical insetcomponent 602 integrated into a disposable bioreactor bag and removablyattached to a reusable sensor assembly 606 which houses theelectro-optical components, similar to the other illustratedembodiments. The disposable bioreactor bag 604 includes an access port608 which may be connected to a fluid circuit, tubing, etc. The interiorof the disposable bioreactor bag 604 may include a solution 610 havingsuspended particles and possibly air 612.

Any of the aforementioned optical bench designs may be integrated with adisposable bioreactor bag 604 or other similar container. The opticalbench 602 shown in FIG. 6 has a unitary design. The optical bench mayinclude in its unitary construction light blocks to prevent thetransmission of light through unintended areas of the optical bench 602.The optical bench includes entrance window 612, an emitting window 614,a receiving window 616, and an exit window 418, each window being asurface of said optical bench 602. The emitting window 614 and receivingwindow 616 are located on the side that is exposed to and/or contactsthe optical bench. The emitting window 614 and receiving window 616 areopposing, facing windows. Located between the emitting window 614 andreceiving window 616 is the scattered light window 620. The opticalbench or bench module 602 may be made of any optically clear materialwhich permits the transmission of electromagnetic radiation, such as abeam of light.

The bioreactor bag 604 is shown in FIG. 6 releasably attached to thereusable sensor assembly 606. This provides a modular approach andallows for exchange of bench modular units, much like the otherillustrated embodiments. A docking port in each of the bioreactor bag604 and the sensor assembly 606 facilitates such exchange.

The reusable sensor assembly 606 includes a printed circuit board 622 onwhich electro-optical components are mounted. A energy beam source 624,which may be a laser diode, LED, or other source of electromagneticradiation, is mounted onto the flat printed circuit board 622. Theenergy beam source 624 is shown mounted vertically such that the energybeam 626 which originates from the energy beam source has an originationvector which is perpendicular to printed circuit board 622 and thecomponents mounted thereon. The other components include one or morescattered light photo diode detectors 628 a, 628 b, and 628 c and areference photo diode detector 630. The scattered light photo diodedetectors 628 a, 628 b, and 628 c, reference photo diode detector 438,and the energy beam source 428 may be collinearly arranged on theprinted circuit board 622.

Adjacent the energy beam source 624 in this embodiment is a lens 632.Located along the optical path from the lens 632 is an aperture disk634. The energy beam source 624, lens 632 and aperture disk 634 are heldin optical alignment by optical alignment bezel 636.

Optically opaque walls 638 and 640 of the sensor assembly 606 separateand optically insolate the components. The scattered light photo diodedetectors 628 a, 628 b, and 628 c are separated from the energy beamsource 624 by opaque wall 438. Likewise, the scattered light photo diodedetectors 628 a, 628 b, and 628 c are separated from the reference photodiode detector 630 by opaque wall 640.

The optical path of the energy beam 626 originates at the energy beamsource 624. The originating vector of the energy beam 626 is vertical,though it is contemplated that the energy beam 626 may be at anotherangle via a mirrored surface contained within the sensor assembly 606.The energy beam 626 travels though a focusing lens 632 and aperture disk634. The aperture disk 634 includes a small aperture which limits thediameter of the energy beam 626.

The energy beam 626 enters the optical bench or bench module 602 throughentrance window 612. The energy beam 626 is then reflected off theinternal reflective surface 642 and travels at an approximately 90degree angle from its originating vector. The angle may vary accountingfor the refractive indexes of the material used and the fluid 610contained within the bioreactor bag 604. The energy beam 626 exits thebench 602 through the emitting reflector window 614 on thefluid-contacting side of the bench 602. The energy beam 626 then travelsthrough the fluid 610, generally parallel to the scattered light window610. As the energy beam 626 travels through the fluid 610 it may bereflected or scattered by particles within the fluid. This scatteredlight (represented by arrows 644) may pass through the scattered lightwindow 620.

The energy beam portion 626 that travels unabated, unimpeded, orun-reflected through the fluid 620 passes through the receivingreflector window 616 of fold mirror 324. The energy beam 626 isreflected approximately 90 degrees downward by the internal reflectorsurface 646. The reflected energy beam 626 travels downward through theexiting window 618 of the optical bench 602. The remaining portion ofthe energy beam 626 strikes reference photo detector 630. The referencephoto detector 630 monitors the transmitted laser light and acts as areference detector, i.e. it detects and measures the intensity of theenergy beam 626 that traveled unabated through the bioreactor bag 604.

The scattered light 644 which passes through scattered light window 620is detected and measured such as by one or more scattered light photodetectors 628 a, 628 b and 628 c, as illustrated.

When used in the turbidity sensor context, the turbidity of the fluid610 is determined by comparing the ratio of the measurements made by thereference detector 622 to the photo scattered light detectors 628 a, 628b, and 628 c.

The embodiments described herein are capable of monitoring solutionturbidity in the range from 0.1 to 1000 NTU. The lower detection limitis 0.05 NTU, and associated noise level is 0.01 NTU. FIG. 7 shows theratiometric laser pulse turbidity response in the 1.0 to 1000 NTU rangewhen utilizing the embodiments described herein. As stated above,analytical signal, derived from the detected scattered light ofsuspended solution particulates, is generated within the space definedby the diameter of the energy beam 404 as it transverses the fluidconduit or bioreactor bag and the distance between the two opposingemitting reflector windows and receiving reflector window. If thereceiving reflector is absent, as with some embodiments, then the signalis based on the length of the scattered light window of the opticalbench.

Using the ratiometric approach, the measurements of scattered lightdetectors is compared against the measurements of the reference photodetector (scattered light detector/reference detector). The ratiometricapproach provides a means for removing the effects of solution colorand/or protein adsorption on any of the windows of the optical bench(e.g. the scatter light window 420). Testing has shown that using theratiometric approach, the response is generally linear for a giventurbidity of the solution when the turbidity is between 1 to 1000 NTU.

FIG. 8 shows the ratiometric laser pulse turbidity response in the 0.1to 10 NTU range when utilizing the embodiments described herein. Again,testing has shown that using the ratiometric approach, the response isgenerally linear for a given turbidity of the solution when theturbidity is between 0.1 to 10 NTU.

Sensor accuracy and precision are primarily limited by the performancespecifications of the energy beam sources, photo detectors andassociated electronics. The sensor accuracy is optimized through afactory calibration of the assembled sensor PCB containing theoptic-electronic components, typically photo detectors and laser diode.The sensor accuracy is further optimized by calibrating the operationalturbidity sensor. A NIST-traceable calibration solution of knowturbidity is pumped through the operational sensor assembly duringcalibration. The calculated and sensor-specific calibration factor,values and zero-offset and are stored in the gamma-stable sensor memorydevice (such as an EEPROM or FRAM) for later recall during sensorfield-use.

The present invention also includes a method of calibrating a turbiditysensor as illustrated in FIG. 9. The sensor monitor and associatedfirmware allows factory calibration of the electro-optical sensorassembly, the disposable fluid conduit, disposable bioreactor bag, ordisposable container, as well as the factory calibration of the completeturbidity sensor assembly and disposable fluid conduit or containermated together. NIST-traceable standard turbidity solutions are used forfactory calibration. A monitor-based algorithm calculates and stores ina memory device (such as an EEPROM) a turbidity calibration curve interms of Nepholemetric Turbidity Units (NTU) by utilizing the knownvalue of the standard turbidity solution, the measured turbidity sensorsignal taken, and taking into account the calibration data of the fluidconduit tube and the electro-optical subassembly.

In the method embodiment of FIG. 9, a disposable conduit tube orcontainer has an inlet for receiving a fluid is provided or utilized ina first action 902. The disposable conduit tube or container may bemated to a sensor assembly as described herein. The sensor assembly hasan electromagnetic radiation source as well as one or more photodetectors. The photo detectors are sensitive to and can measure theintensity of electromagnetic radiation created by the source.

A portion of the turbidity sensor is integrated within the interiorcavity of a disposable conduit tube or container. The turbidity sensorincludes one or more reflective surfaces. At least one of reflectivesurfaces of the turbidity sensor is located within the cavity of thetube or container. The reflective surfaces may be internal reflectorsurfaces of an optical bench as described herein.

A fluid with a known concentration of suspended particles (a standardturbidity solution) is delivered to the interior cavity through aninlet, such as an access port or end of a fluid-conduit tube in a secondaction 904. As a result, the fluid comes in contact with the turbiditysensor. Electromagnetic radiation, such as a energy beam or laser beamwith a wavelength of 660 nm or 220 nm, is then activated as illustratedat 906. The electromagnetic radiation is reflected off of at least oneof said reflective surfaces, illustrated as action 908, and thereafterthe electromagnetic radiation travels through the fluid, noted at 910.At least a portion of electromagnetic radiation which is reflected bythe suspended particles and is measured, noted at 912. The remainingportion of the electromagnetic radiation which passed through the fluidin an unimpeded or un-reflected condition is measured, noted at action914.

Based on the two measurements (the portion of electromagnetic radiationwhich was reflected by the suspended particles and the portion of theelectromagnetic radiation which passed through the fluid in anunimpeded) one or more calibration values are calculated, noted at 916.The calculation may be based on a ratiometric comparison of the portionof electromagnetic radiation which was reflected by the suspendedparticles and the portion of the electromagnetic radiation which passedthrough the fluid in an unimpeded fashion. An algorithm calculates aturbidity calibration curve in terms of Nepholemetric Turbidity Units(NTU) by utilizing the known value of the standard turbidity solution,as well as the measured turbidity sensor signals.

The calculated and sensor-specific calibration factor, calibrationvalues and zero-offset are stored as noted at 918 in the gamma-stablesensor memory device (such as an EEPROM or FRAM) for later recall duringsensor field-use. Other data, such as the calibration curve, flowcellID, and calibration date, may also be in memory device. The memorydevice is associated with or contained within, fluid conduit assembly orthe sensor assembly as, for example, shown in FIG. 2. When the turbiditysensor is connected to a readout device, processor, computer, sensormonitor, or user interface, the stored calibration curve and othervalues are accessible and used to instruct readout device, computer,etc. as to the calibration as well as calibrate other associateddevices.

The aforementioned embodiments include a selection of novel sensormaterials, innovative circuit designs which separate the analog anddigital circuits, labeling to preserve sensor-specific information, anda user interface that includes supporting software and procedures toaccommodate, retrieve, interpret and calculate sensor-specificinformation. These materials, circuits, and labeling, are designed towithstand the conditions of the sterilization methods used by thebiopharmaceutical industry. However, gamma or electron-beam irradiationmay render a memory chip or EEPROM non-functional, and it iscontemplated that the flowcell assemblies, bioreactor bags, and reusablesensor assemblies may be manufactured without a memory chip. In theseembodiments, the analog components are manufactured and assembled intosensors. The sensors are validated, and the sensor specific informationis then printed on the sensors or shipping bags in print, RFID orbarcode form. The sensors are then placed in shipping bags or othersuitable containers, irradiated via gamma rays or electron-beam, andthen delivered to the user. The sensor-specific information is enteredinto the user interface either by a barcode scanner or the like, ormanually by the user. This embodiment saves the costs associated withotherwise including the memory chip with the sensor.

The aforementioned embodiments include a selection of novel sensormaterials, innovative circuit designs which separate the analog anddigital circuits, labeling to preserve sensor-specific information, anda user interface that includes supporting software and procedures toaccommodate, retrieve, interpret and calculate sensor-specificinformation. These materials, circuits, and labeling are designed towithstand the conditions of the sterilization methods used by thebiopharmaceutical industry.

As shown in FIG. 10, the present invention also includes measuringmethods. FIG. 10 illustrates the method of measuring the turbidity of afluid utilizing a disposable fluid conduit, disposable bag or containerand a reusable sensor assembly. The reusable sensor assembly isconnectable to a disposable fluid conduit, disposable bag or container.The reusable sensor assembly includes the disposable fluid conduit,disposable bag or container.

A disposable conduit or container is mated to a sensor assembly as shownat action summary 1002. The disposable conduit or container has an inletand interior cavity for receiving a fluid. The disposable conduit orcontainer also has an integrated optical bench with any of the featuresdescribed above. The optical bench may be comprised of one or morereflective portions or surfaces, the reflective portions or surfaceslocated within the interior of the disposable conduit or container orextending toward the interior of said conduit or container.

A fluid having suspended particulates and an unknown turbidity isdelivered into the interior cavity of the disposable conduit orcontainer, noted at 1004. Electromagnetic radiation, such as a energybeam or laser beam with a wavelength of 660 nm or 220 nm, is thenactivated, noted at 1006. The electromagnetic radiation is reflected offof at least one of said reflective surfaces, depicted at 1008, andthereafter the electromagnetic radiation travels through the fluid as at1010. At least a portion of electromagnetic radiation which is reflectedby the suspended particles in the fluid and is measured as at 1012 bythe sensor assembly. The remaining portion of the electromagneticradiation which passed through the fluid in an unimpeded or un-reflectedcondition is measured as at 1114 separately by the sensor assembly.

Calibration values, such as a zero-offset, or a calibration curve basedvalue are downloaded from a memory device associated with the disposableconduit or bag and/or the sensor assembly as at 1016. Based on the twomeasurements (the portion of electromagnetic radiation which wasreflected by the suspended particles and the portion of theelectromagnetic radiation which passed through the fluid in anunimpeded) and one or more calibrations values, the turbidity of thefluid is determined, noted at 1018. The turbidity calculation may bebased on a ratiometric comparison of the portion of electromagneticradiation which was reflected by the suspended particles and the portionof the electromagnetic radiation which passed through the fluid in anunimpeded offset by the calibration values or the calibration curve. Theturbidity may then be displayed or stored by a readout device, computer,user interface, etc., as noted at 1020.

It will be understood that the embodiments of the present inventionwhich have been described are illustrative of some of the applicationsof the principles of the present invention. Numerous modifications,including stated and unstated combinations of features, may be made bythose skilled in the art without departing from the true spirit andscope of the invention.

The invention claimed is:
 1. A sensor for measuring one or moreproperties of a fluid, comprising: (a) a reusable sensor assemblyincluding a housing supporting a source of electromagnetic radiation anda detector for measuring electromagnetic radiation, the source ofelectromagnetic radiation generates and directs electromagneticradiation; a disposable flow cell, the disposable flow cell and reusablesensor assembly being configured to dock together, the disposable flowcell comprising a conduit or container having an interior that containsthe fluid when in use, an exterior, an optically clear portion locatedbetween the interior and exterior of said conduit or container, and anoptical inset component including at least one reflective surface atleast partially within the conduit or container; whereby electromagneticradiation from the electromagnetic radiation source of the reusablesensor assembly, when docked with the disposable flow cell, reflects offsaid reflective surface of the disposable flow cell that directs theelectromagnetic radiation along a path that is initially generallyparallel to the optically clear portion, then reflects off one or moreparticulates of the fluid when located in the interior of said conduitor container, and thereafter passes through said optically clear portionand to said electromagnetic radiation detector of the reusable sensorassembly.
 2. The sensor of claim 1, comprising a plurality of saidelectromagnetic radiation detectors, at least one of which is areference detector for measuring electromagnetic radiation generated bysaid electromagnetic radiation source and at least another of which is adetector for measuring electromagnetic radiation generated by saidelectromagnetic radiation source that had impinged upon a particle inthe conduit or container; and said electromagnetic radiation source,reference detector, and measuring detector are collinearly arranged. 3.The sensor of claim 1, wherein the disposable flow cell conduit orcontainer includes an inlet and an outlet, the disposable flow cellbeing configured to accommodate flow of the fluid from the inlet, to theoptical inset component and to the outlet.
 4. A system for measuringturbidity of fluid, comprising: a. a reusable sensor assembly having ahousing component, said housing component enclosing at least one sourceof electromagnetic radiation for generating electromagnetic radiationand at least one reference detector for measuring electromagneticradiation, said housing component having a portion which permits thetransmission of electromagnetic radiation; b. a disposable flow cellconfigured to dock with the reusable sensor assembly, the disposableflow cell including a conduit or container having an interior thatcontains the fluid when in use, an exterior, and an optical insetcomponent including at least one reflective surface at least partiallywithin the conduit or container, and at least one optically clearportion positioned between the interior and the exterior of the conduitor container, whereby electromagnetic radiation from the source ofelectromagnetic radiation reflects off said reflective surface andreflects off one or more particulates when located in the interior ofsaid conduit or container, and thereafter passes through said opticallyclear portion; and c. when the disposable flow cell and said reusablesensor assembly are docked together said optical inset component andsaid housing component are optically aligned.
 5. The sensor of claim 4,wherein the disposable flow cell conduit or container includes an inletand an outlet, the disposable flow cell being configured to accommodateflow of the fluid from the inlet, to the optical inset component and tothe outlet.
 6. A method of measuring turbidity of a fluid, comprising:a. providing a disposable conduit or container, the conduit or containerhaving an interior cavity for a fluid, the conduit or container having adocking port and an inset optical component, the inset optical componenthaving one or more reflective surfaces at least partially within theconduit or container, the reflective surfaces extending toward theinterior of the conduit or container; b. providing a reuseable sensorassembly having an electromagnetic radiation source and detectorsupported by a housing having a housing docking port; c. docking thedisposable conduit or container to the sensor assembly housing byengaging together the inset optical component docking port and thehousing docking port; d. delivering a fluid into the interior cavity ofthe conduit or container, the fluid having particulates; e. directingelectromagnetic radiation from the radiation source; f. reflecting theelectromagnetic radiation off one of the reflective surfaces of theinset optical component along a path that is initially generallylongitudinal with respect to the conduit or container, whereby theelectromagnetic radiation is directed through the fluid and impinges atleast one particle within the fluid while the fluid is within theconduit or container; g. measuring the electromagnetic radiationreflected by the particulates in the fluid; and h. calculating theturbidity of the solution.
 7. The method of claim 6, further includingmeasuring the electromagnetic radiation that passed through the fluid inan unimpeded or un-reflected condition and including data generatedthereby in said calculating.
 8. The method of claim 7, furthercomprising retrieving a calibration value from a memory deviceassociated with the disposable conduit or container.
 9. The method ofclaim 8, wherein said calculating the turbidity of the solution utilizesthe results of measuring the electromagnetic radiation reflected by theparticulates in said fluid and measuring the electromagnetic radiationwhich passed through the fluid in an unimpeded or un-reflected conditionand the retrieved calibration value.
 10. The method of claim 6, furtherincluding flowing the fluid within the conduit or container at the insetoptical component in a direction generally longitudinal with respect tothe conduit or container.
 11. The method of claim 10, wherein saidflowing of fluid is generally parallel to the reflecting path of theelectromagnetic radiation that is generally longitudinal to the conduitor container.
 12. A method of calibrating a turbidity sensor,comprising: a. providing a disposable conduit or container, the conduitor container having an interior cavity for receiving a fluid, an inletto said cavity and an inset optical component, the inset opticalcomponent having one or more reflective surfaces at least partiallywithin the conduit or container, the reflective surfaces extendingtoward the interior cavity; b. providing a reuseable sensor assemblyhaving an electromagnetic radiation source and detector supported by ahousing having a housing docking port; c. docking the disposable conduitor container to the sensor assembly housing by engaging together theinset optical component docking port and the housing docking port; d.delivering a fluid with a known concentration of particulates to theinterior cavity through the inlet; e. reflecting electromagneticradiation off one of the reflective surfaces of the inset opticalcomponent along a path that is initially generally longitudinal withrespect to the conduit or container, whereby the electromagneticradiation is directed through the fluid and impinges at least oneparticle within the fluid while the fluid is within the cavity; f.measuring the electromagnetic radiation reflected by the particulates inthe fluid; and g. calculating one or more calibration values based onthe result of measuring of the electromagnetic radiation reflected offthe particulate in the fluid.
 13. The method of claim 12, furtherincluding measuring the electromagnetic radiation that passed throughthe fluid in an unimpeded or un-reflected condition, and the calculationis further based on said measuring of the electromagnetic radiationwhich passed unimpeded/un-reflected.
 14. The method of claim 12, furtherincluding storing one or more calibration values in a memory deviceassociated with the disposable conduit or container.
 15. The method ofclaim 12, further including flowing the fluid within the conduit orcontainer at the inset optical component in a direction generallylongitudinal with respect to the conduit or container.
 16. The method ofclaim 15, wherein said flowing of fluid is generally parallel to thereflecting path of the electromagnetic radiation that is generallylongitudinal to the conduit or container.